A composite image forming apparatus (called as an MFP) having plural functions such as a copying function, a scan function and a print function can print image data inputted from a network-connected external equipment (for example, a personal computer).
The image data inputted from the external equipment is PDL (Page Description Language) data which a printer (printer engine) of the image forming apparatus can understand.
The image forming apparatus uses a built-in RIP (Raster Image Processor) to convert the PDL data inputted from the external equipment into bitmap format image data which the printer can understand (rendering processing). The bitmap format image data includes image data Y corresponding to a yellow image, image data M corresponding to a magenta image, image data C corresponding to a cyan image, and image data K corresponding to a black image.
As an image forming medium of the image forming apparatus as stated above, there is a long size (also called as a banner size) thin and long print sheet.
However, in the image forming apparatus, the image data for one page is created for each page and is stored in a memory, and the image data for one page in the memory is sequentially supplied to the printer. In the case of so-called as banner printing in which the long size print sheet as stated above is used, since the size of the image data for one page is large, a large capacity memory is required.
However, the memory is used not only in the print function but also in other functions. In the case where the remaining capacity of the memory is small, the banner printing using the long size print sheet becomes impossible.